This invention is directed to a method for providing flow control of heat activated expandable or non-expandable sealants which are used to seal gaps or cavities in parts such as components in automotive vehicles, and more particularly, to such a method which utilizes a sealant in combination with a flow control agent to modulate the flow of the sealant upon heating.
In the manufacture of automotive vehicles, many body components include cavities which require sealing in order to block the passage of dust, moisture, and air (fumes) which can cause corrosion of the body parts. Such sealants are also used to block the passage of noise through the openings. Heat activated sealants are known in the automotive industry for the purpose of filling such gaps and voids. For example, expandable sealants may be formed into a desired configuration which is adapted to be placed within a body cavity or between two parts so that when the part is subjected to a paint baking operation or other process at elevated temperatures, the shaped sealant expands to an extent that the cavity or area between the parts is filled or sealed. Such heat activated sealants are typically comprised of thermoplastic or thermosetting materials which may contain a blowing agent which is activated upon heating such that the sealant expands and flows into the gaps.
Heat activated expandable sealants currently in use are typically used to bridge or seal gaps which are less than about 8 to 10 mm. However, when such gaps are greater than about 10 mm (up to 100 mm), it is difficult to achieve proper flow as the adhesive tends to flow excessively, causing unsightly “stalactites”. In addition, the sealant is often unable to expand or flow sufficiently to bridge the larger gaps without excess thinning or blow-out in the gap being sealed.
It would be desirable to be able to better control the flow of heat activated sealants to eliminate the problems of excessive flow or sag. Accordingly, there is a need in the art for a method of controlling flow of heat activated sealants.